Abstract: The alkyl imidazolium-based ionic liquids, 1-n-butyl-3-methylimidazole methyl carbonate (n-BMIMOCO2Me) and 1,2-dimethyl-3-ethylimidazole ethyl carbonate (EMMIMOCO2Et), were synthesized from N-methylimidazole, 1,2-dimethylimidazole and carbonates. Reacting with HBF4 and HPF6 at room temperature, n-BMIMOCO2Me and EMMIMOCO2Et were converted into four ionic liquids: 1-n-butyl-3-methylimidazolium tetrafluoroborate (n-BMIMBF4), 1-n-butyl-3-methylimidazolium hexafluorophosphate (n-BMIMPF6), 1,2-dimethyl-3-ethylimidazolium tetrafluoroborate (EMMIMBF4), and 1,2-dimethyl-3-ethylimidazolium hexafluorophosphate (EMMIMPF6). The six ionic liquids were characterized and analysed by FT-IR, 1H-NMR, ESI-MS and DSC. Environmental pollution was avoided by the green chemical synthetic method in comparison with the traditional two-step synthesis.